1. What is “stray voltage?”

Stray voltage is a natural phenomenon that has been researched for the past 40 years. It usually occurs when a farm animal makes contact with metal equipment that is touching the “neutral” wire on a farm’s electrical system. The neutral wire carries very low levels of voltage back to the transformer that supplies electricity to the farm. This voltage is the result of resistance on the wire to electrical current flowing through the wire.

2. Why is this a problem on dairy farms?

If an animal is touching metal equipment in the right conditions, a small amount of the current on a neutral line can flow though the animal into the ground. Usually, the amount of this “stray voltage” is not enough to cause physical or behavioral changes in the animal.

3. Is stray voltage a new problem?

Multiple studies funded by federal and state agencies, utilities and dairy associations, have found that stray voltage can be kept to levels where dairy livestock health and production are not affected. This was substantiated in the United States Department of Agriculture Handbook 696, 1991, Effects of Electrical Voltage/Current on Farm Animals–How to Detect and Remedy Problems and other national and international research.

4. Why have I heard so much about stray voltage in Idaho lately?

In the early 1990s, a large number of dairy operations began moving into Idaho.

5. Is stray voltage only found on dairy farms?

Stray voltage can originate from sources both off-farm and on-farm.

6. How do I know if there is stray voltage on my property?

Idaho Power’s trained stray voltage technicians work with our customers to address stray voltage concerns. If you would like assistance with a possible stray voltage problem, call Idaho Power’s customer service center at 1-800-488-6151or 388-2323 in the Treasure Valley and ask to speak with a Power Quality Engineer. Our staff will complete a free on-site investigation and work directly with you to diagnose and remedy stray voltage issues, which are often a shared responsibility.

7. What is an acceptable level of stray voltage?

Idaho Power has established a threshold level of 1 volt at the livestock-point-of-contact. This is slightly less than the voltage of a single standard flashlight battery (1.5 volts) and is consistent with U.S. Department of Agriculture findings.

If levels above 1 volt are detected, the company will determine the degree to which the levels can be attributed to the company’s system and the degree to which they can be attributed to the customer’s electrical system. Our stray voltage technicians will take necessary steps to remedy any issues with the system and advise the customer of possible actions to address those originating at the customer’s facility.

8. What can dairy farmers do to reduce the possibility of stray voltage?

The presence of stray voltage at a dairy operation is impossible to eliminate without giving up features of the system’s design that address reliability, equipment protection and the safety of humans and animals. However, there are options available to reduce stray voltage to the point that it has no adverse effect on livestock or livestock operations. We make every effort to ensure that such efforts result in the protection of all customers’ best interests.

By request, we will install a neutral isolator at a facility, completely separating the customer’s grounded system from the broader and more extensive grounding system of Idaho Power. For more information on the risks associated with this option, please call Idaho Power’s customer service center at 1-800-488-6151 or 388-2323 from the Treasure Valley and ask to speak with a Power Quality Engineer.

9. How can I learn more about stray voltage?

We recognize the importance of making information and educational opportunities regarding stray voltage available to farmers, electricians and other interested parties. Idaho Power is committed to keeping ourselves and our customers informed about stray voltage-related scientific and regulatory developments. We maintain a library of publications relevant to stray voltage research, legislation and related issues. This information is accessible to Idaho Power’s customers, employees and other interested parties at the company’s corporate library at 1221 W. Idaho St., Boise.

In addition to information available from Idaho Power representatives in your community, the company recommends the USDA Handbook 696(PDF)
on Stray Voltage/Current, which provides a complete overview of the subject. Please note that this brochure may take up to 17 minutes to download on a 56k modem. The handbook may also be obtained from our corporate library by calling 208-388-2316.

For more information regarding stray voltage, contact Idaho Power at 1-800-488-6151 or 388-2323 from the Treasure Valley.